NSA Director Keith Alexander told a Senate panel that his agency's program did indeed protect American's privacy while gathering data on terrorist activity. Alexander told lawmakers he wants to declassify more details to reassure everyone the programs are legal and effective.

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The head of the National Security Agency yesterday made his first public appearance since details leaked about two surveillance programs run by the NSA. General Keith Alexander, who's also in charge of the military's Cyber Command, testified before the Senate Appropriations Committee.

And as NPR's Ailsa Chang reports, he wants to declassify more details to reassure Americans the programs are both legal and effective.

AILSA CHANG, BYLINE: General Keith Alexander needed to present himself as the man with absolutely nothing to hide. He was polite, almost deferential. He locked into solid eye contact with each senator who addressed him. And he kept hammering home one main talking point: It was time for the American people to get some answers.

(SOUNDBITE OF SENATE HEARING)

GENERAL KEITH ALEXANDER: The perspective is that we're trying to hide something, because we did something wrong. We're not. We want to tell you what we're doing and tell you that it's right, and let the American people see this. I think that's important. But I don't want to jeopardize the security of our country or our allies.

CHANG: The man who wants to give the world answers has one fundamental problem: He operates in a classified world. So the dilemma is deciding what to declassify, so as to restore the American public's shaken confidence. For example, take this question from Democrat Jeff Merkley of Oregon, who pointed out phone data can only be sought under the Patriot Act if it's relevant to an authorized investigation.

ALEXANDER: I do think what we should do as part of perhaps the closed hearing tomorrow, walk through that, with the intent of taking what you've asked and seeing if we can get it declassified and out to the American people so they see exactly how we do it. Because I do think that should be answered.

CHANG: Democratic Senator Patrick Leahy from Vermont wanted to know exactly how many terrorism cases were disrupted or discovered with the help of the phone records.

(SOUNDBITE OF SENATE HEARING)

ALEXANDER: It's dozens of terrorist events that these have helped prevent.

SENATOR PATRICK LEAHY: OK, so dozens.

CHANG: That's a pretty vague number, but Alexander said he'd give senators a specific list during a closed briefing today. Declassifying that list for the general public may take longer, the general said.

Now, there were some pressing questions Alexander could answer on the spot, like one about the leaker, Edward Snowden. Here's Republican Susan Collins of Maine.

(SOUNDBITE OF SENATE HEARING)

SENATOR SUSAN COLLINS REPUBLICAN, MAINE: Mr. Snowden claimed that due to his position at NSA, he could tap into virtually any American's phone calls or emails. True or false?

ALEXANDER: False. I know of no way to do that.

CHANG: But for all those convinced that the federal government is invading their privacy, here's the solace Alexander offers.

(SOUNDBITE OF SENATE HEARING)

ALEXANDER: I do think what we're doing does protect American civil liberties and privacy. The issue is, to date, we've not been able to explain it because it's classified.

CHANG: Many Americans are going to be waiting for that explanation to be declassified, before feeling any better about this whole thing.

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